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#26

Jaros
Moderator
From: S.E.Qld., QLD
Joined: 11 August 2013
Posts: 11,206
Moderator
24 January 2019 02:19 pm

Gunna be a busy boy. Shouldn't be long now before you're out there.


F1A4M2, Exterra 705 Gold, Ace 250, Goldrat 8" Dreammat River Sluice.

1 user likes this post: Baldy

#27

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
24 January 2019 05:09 pm

Hi all,
A question without notice on dual battery installations.
Can someone explain, in simple english, why the need for DC to DC chargers?

Thanks in advance

#28

Jaros
Moderator
From: S.E.Qld., QLD
Joined: 11 August 2013
Posts: 11,206
Moderator
24 January 2019 05:20 pm

This is pretty well explained.

DC-DC BATTERY CHARGERS EXPLAINED
By: David Cook, Photography by: David Cook

Date: 14.09.2015

A DC-DC charger keeps your caravan’s auxiliary battery system operating at peak efficiency for longer when you’re off the grid. David Cook explains how and why.

DC-DC battery chargers explained
A DC-DC charger is effectively a smart-charger for your 12V system
When you start talking 12V electronics, I reckon half the audience switches off and the other half starts digging fox holes, ready for war.

The fact is, 12V electronics are confusing. It is supposed to be about 12V, but the batteries need around 14.4V to charge, are considered 100 per cent charged at 12.8V and only 50 per cent charged at 12.2V.

The confusion is compounded by various battery chemistries, all with different charging regimes and characteristics, and the fact that what works for one vehicle’s setup might not in another vehicle.

Then there’s cable size, assessed in at least four different ways, and a steady flow of new technology. So there’s little surprise vanners wanting to optimise their electrical systems but, beset by conflicting and confusing information, shy away hoping what they already have will do.

BATTERIES
For the purposes of this article, we’ll refer to the batteries in our caravans as house batteries and those in tow vehicles as cranking batteries.

Like all batteries, these supply electricity for our lights, fridges, chargers and other electrical appliances. We can do this off the vehicle’s alternator while driving, off mains power, or via some third form, such as solar or generator, when off the grid.

Our house batteries are (or should be) different to cranking batteries. The former are designed to deliver relatively low levels of electricity over a long period. The most common house batteries are lead acid (deep-cycle), absorbed glass matt (AGM), gel, calcium and now lithium.

House batteries are rated by amp-hours (Ah) – the theoretical capacity to deliver ‘x’ amount of amps in an hour. In a 100Ah battery, for example, this equals 100A for one hour or 5A per hour for 20 hours. In practice, we shouldn’t do that, because discharging a storage battery completely (except lithium) can shorten its life. The manufacturer-recommended level is usually 50 per cent (when the voltage reads 12.2V), though AGMs will survive happily down to 30 per cent (11.85V).

This means that, in a house battery system with one 100Ah battery, you have 50-70A maximum capacity.

CHARGING
Some travellers rely on a cable connection from their vehicle’s alternator-based charging system, with an Anderson plug to connect it at the hitch point. However, while it is possible to fully charge a battery off an alternator, because the rate of charge declines as the voltage in thebattery approaches that of the charging system, it rarely exceeds about 70 to 75 per cent, even after a full day’s driving. And because our house batteries are at the end of 8-10m of cable, along which you will get voltage drop, that can be even less.

So our 100Ah deep-cycle battery that ran down to 50Ah after a few days’ use may only return to 70Ah for our next night’s camp, leaving us with a nominal 20Ah of useable capacity (70Ah minus our 50Ah minimum charge).

Fuel efficient low (or variable) voltage alternators found in modern 4WDs compound the issue, producing as little as 13.8V compared to 14.4V produced in earlier generation vehicles. There’s even talk of switching off the alternator once the cranking battery is deemed ‘fully charged’.

So what can we do?

BASIC SETUP
Many factors can assist. Firstly, limit losses by:

using decent-sized cable from the alternator to the house battery (minimum 6B&S/13.5mm² – that’s close to a pencil in diameter) and replace any of the 6mm cable usually offered
using genuine Anderson plugs (not cheap clones, usually sold as ‘Anderson-style’ plugs)
crimping and soldering all connections.
Secondly, install a DC-DC charger adjacent to the house battery.
DC-DC CHARGERS
A DC-DC charger is effectively a smart-charger for your 12V system. It isolates the house battery system from the alternator, so that the vehicle’s computer management system sees it as something like a set of lights. At the same time, it boosts the charge at the house battery from as little as 9V back up to 14.4V (or higher, if required) to maximise charging capacity, delivering it in stepped form, like your smart mains charger, achieving close to 100 per cent charge after a day’s driving.

Most DC-DC chargers also act as solar regulators, relocating what’s traditionally been a separate item on your solar panel to a better position – adjacent to the house battery. And these are no ordinary regulators, but maximum power point trackers (MPPT) that optimise your solar panels’ performance.

Most DC-DC chargers draw a higher rate of amperage from the alternator than would be supplied if you let the alternator ‘push’ down the cable. This can be up to 40A or more per hour, quickly replenishing the house battery system.

Complete battery management systems (BMS) are new to the market and incorporate a mains charger, a DC-DC charger and MPPT solar regulator.

These generally come with a high-tech battery monitoring panel and, while expensive, are simple to install, requiring no post-manufacturer wiring between multiple units.

DC-DC chargers benefit from 6B&S/13.5mm² cabling (the conductor, not the conductor plus insulation, which is how most cable is sold). They work with smaller cable, but as the voltage drop through smaller cable increases, the heat produced reduces its conductivity, forcing the charger to work harder, drawing more current and increasing heat. This can continue to the point where the demand exceeds the alternator’s capacity to supply. The energy dissipates as heat is wasted.

Installing the charger near the house battery overcomes much of that voltage drop, while adhering to the manufacturer-recommended minimum clearance assists in dissipating heat.

DC-DC chargers increase the likelihood of your batteries arriving in camp at close to a full charge, minimises damage to your house battery system from over discharging and, in my opinion, should be fitted as mandatory or at least offered as an option on every camper and caravan sold in Australia.


F1A4M2, Exterra 705 Gold, Ace 250, Goldrat 8" Dreammat River Sluice.

2 users like this post: goody2shoes, Ded Driver

#29

Ded Driver
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From: West of the Border, WA
Joined: 27 May 2018
Posts: 1,936
Member
24 January 2019 06:09 pm

update: Im very happy with my system so far. Lead Crystal battery + Projecta 45A DC-DC charge controller + 100W solar panel
Im finding the solar panel more than covers my fridge on sunny days, and tops up the battery. I have a dual voltmeter on the circuit shows me battery & solar input.
I have a manual circuit breaker under the bonnet between the 2 batteries (for alternator charging), & i flick this in once a week or so to ensure ther battery gets a full current top-up as required. Im still procrastinating on whether or not to install the solenoid that I have .... I like manual operation on most stuff, plus still need a breaker/fuse anyway.
An interesting point on the LC battery ... my electronic diagnostic unit (analyses battery & alternator charging, & has proven correct on many occassions now) cannot analyse the Lead Crystal Battery, I assume due its different chemical makeup.


APLA member, GPX4000, modded SD2100, XTerra705, GM1000, Whites MXT Pro, Nokta Pointer, sP01 Enhancer, Garmin GPSMAP 64S, kti PLB, a map, all sorts of coils & a cupla buckets full of hope & enthusiasm

#30

HeadsUp
Banned
From: Sydney, NSW
Joined: 17 April 2013
Posts: 3,012
Banned
24 January 2019 09:41 pm

Goldchaser1 wrote:

The lithiums arent that expensive,i bought 4 of these for $640.... cool
https://www.evworks.com.au/calb-ca100

Did you get a BMS ?

(battery charge management system)

If putting multiple LiPo in series the charge will become imbalanced and they will kill each other.

cry


On a mission to rescue as many gold nuggets as i can before those poor souls get washed out to sea . GPX5000 smilemaker , self built highbanker and enthusiastic shovel

#31

Dog Ranger
Member
Joined: 07 December 2018
Posts: 150
Member
24 January 2019 11:31 pm

Ded Driver wrote:

update: Im very happy with my system so far. Lead Crystal battery + Projecta 45A DC-DC charge controller + 100W solar panel
Im finding the solar panel more than covers my fridge on sunny days, and tops up the battery. I have a dual voltmeter on the circuit shows me battery & solar input.
I have a manual circuit breaker under the bonnet between the 2 batteries (for alternator charging), & i flick this in once a week or so to ensure ther battery gets a full current top-up as required. Im still procrastinating on whether or not to install the solenoid that I have .... I like manual operation on most stuff, plus still need a breaker/fuse anyway.
An interesting point on the LC battery ... my electronic diagnostic unit (analyses battery & alternator charging, & has proven correct on many occassions now) cannot analyse the Lead Crystal Battery, I assume due its different chemical makeup.

Given your running a DC D.C. unit any specific reason for manually disconnection from alternator? Just curious?

3 users like this post: HeadsUp, ctxkid, Ded Driver

#32

HeadsUp
Banned
From: Sydney, NSW
Joined: 17 April 2013
Posts: 3,012
Banned
24 January 2019 11:44 pm

a small point if you are buying a solar panel and DC-DC charger .

I have seen Solar panels claimed to be for a 12 volt system that put out up to 31 volts but some DC-DC chargers state their maximum open circuit voltage is 23 volts so check both specs before buying and before you install them.

From memory the CTEK 250D for example is 23 VDC solar input while Redarc is 36 VDC.

Do ya homework !


On a mission to rescue as many gold nuggets as i can before those poor souls get washed out to sea . GPX5000 smilemaker , self built highbanker and enthusiastic shovel

#33

ctxkid
Member
From: Up Ship Creek
Joined: 12 April 2018
Posts: 2,146
Member
25 January 2019 07:10 am

Solar panels for the most labeled as having a 21v open circuit voltage


...................................................Such is life........................................................
Oldest Copper coin 1799 left seated half penny, Oldest Silver 1834 Shilling

#34

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
25 January 2019 08:18 am

Jaros wrote:

This is pretty well explained.

BASIC SETUP
Many factors can assist. Firstly, limit losses by:

using decent-sized cable from the alternator to the house battery (minimum 6B&S/13.5mm² – that’s close to a pencil in diameter) and replace any of the 6mm cable usually offered
using genuine Anderson plugs (not cheap clones, usually sold as ‘Anderson-style’ plugs)
crimping and soldering all connections.
Secondly, install a DC-DC charger adjacent to the house battery.
DC-DC CHARGERS
A DC-DC charger is effectively a smart-charger for your 12V system. It isolates the house battery system from the alternator, so that the vehicle’s computer management system sees it as something like a set of lights. At the same time, it boosts the charge at the house battery from as little as 9V back up to 14.4V (or higher, if required) to maximise charging capacity, delivering it in stepped form, like your smart mains charger, achieving close to 100 per cent charge after a day’s driving.

Thanks for that Jaros.

An interesting read.

It's a concern that the author advocates both crimping and soldering a connection, especially in high current connections. (If I've misunderstood his statement then many others may also hmm )

My original question could have been better worded. I was referring to a dual battery system where both batteries are installed under the bonnet as I'd misread the OP as saying that was his intent. In my scenario, there is no apparent cost efficient benefit in fitting a DC-DC charger.

Last edited by bicter (25 January 2019 08:20 am)

#35

Dog Ranger
Member
Joined: 07 December 2018
Posts: 150
Member
25 January 2019 08:47 am

Don't know what your scenario is but probably safe to say that regardless of second battery location, one still benefits from an efficient charge controller?
That fact makes the whole system more efficient and safe guards your $300 plus battery also thumbsup

#36

ctxkid
Member
From: Up Ship Creek
Joined: 12 April 2018
Posts: 2,146
Member
25 January 2019 09:47 am

Flood solder all connections cool

Here a screen shot of my new controller heart

1548370033_image.jpg

Last edited by ctxkid (25 January 2019 09:50 am)


...................................................Such is life........................................................
Oldest Copper coin 1799 left seated half penny, Oldest Silver 1834 Shilling

1 user likes this post: Ded Driver

#37

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
25 January 2019 10:19 am

Dog Ranger wrote:

Don't know what your scenario is but probably safe to say that regardless of second battery location, one still benefits from an efficient charge controller?
That fact makes the whole system more efficient and safe guards your $300 plus battery also thumbsup

I have a different viewpoint.

In an under bonnet scenario, the DC-DC can be a bottle neck to charge current and adds unnecessary costs as well as introducing an extra failure point (Expensive Fuse) that puts the second battery at risk.
Additionally, it makes it more difficult to connect in parallel for starting when/if required. (Unless, of course, the DC-DC has a bypass mode built in).
This is based on the assumption that a full charge is better for battery longevity than having a regulated voltage applied to the battery and not necessarily achieving full charge with stop/start or short trip driving.
Use of a DC-DC can be justified when the second battery has a charge profile unsuited to paralleling the start battery or other requirements demand it, such as if an unregulated solar panel is required to keep the 2nd battery charged.

There are some very good salesmen out there.

There is no one size fits all design for auxiliary batteries.

#38

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
25 January 2019 10:23 am

ctxkid wrote:

Flood solder all connections cool

Or crimp to the design pressure ensuring the correct cable size for the connector and the correct crimp tool is used.

#39

Jaros
Moderator
From: S.E.Qld., QLD
Joined: 11 August 2013
Posts: 11,206
Moderator
25 January 2019 10:32 am

I still prefer to solder electrical connections--pure and simple -like the oil spray. perfect


F1A4M2, Exterra 705 Gold, Ace 250, Goldrat 8" Dreammat River Sluice.

#40

Dog Ranger
Member
Joined: 07 December 2018
Posts: 150
Member
25 January 2019 11:09 am

bicter wrote:
Dog Ranger wrote:

Don't know what your scenario is but probably safe to say that regardless of second battery location, one still benefits from an efficient charge controller?
That fact makes the whole system more efficient and safe guards your $300 plus battery also thumbsup

I have a different viewpoint.

In an under bonnet scenario, the DC-DC can be a bottle neck to charge current and adds unnecessary costs as well as introducing an extra failure point (Expensive Fuse) that puts the second battery at risk.
Additionally, it makes it more difficult to connect in parallel for starting when/if required. (Unless, of course, the DC-DC has a bypass mode built in).
This is based on the assumption that a full charge is better for battery longevity than having a regulated voltage applied to the battery and not necessarily achieving full charge with stop/start or short trip driving.
Use of a DC-DC can be justified when the second battery has a charge profile unsuited to paralleling the start battery or other requirements demand it, such as if an unregulated solar panel is required to keep the 2nd battery charged.

There are some very good salesmen out there.

There is no one size fits all design for auxiliary batteries.

No argument here ? As said without knowing your set up one can only generalize?
Thanks for the specifics on your set up and it's requirements

#41

ctxkid
Member
From: Up Ship Creek
Joined: 12 April 2018
Posts: 2,146
Member
25 January 2019 11:10 am

bicter wrote:
ctxkid wrote:

Flood solder all connections cool

Or crimp to the design pressure ensuring the correct cable size for the connector and the correct crimp tool is used.

i have seen to many poor crimped connections awful

i'm with Jaros yikes solder rules power perfect

an hey i like the smell of solder playful


...................................................Such is life........................................................
Oldest Copper coin 1799 left seated half penny, Oldest Silver 1834 Shilling

#42

Dog Ranger
Member
Joined: 07 December 2018
Posts: 150
Member
25 January 2019 11:38 am

ctxkid wrote:
bicter wrote:
ctxkid wrote:

Flood solder all connections cool

Or crimp to the design pressure ensuring the correct cable size for the connector and the correct crimp tool is used.

i have seen to many poor crimped connections awful

i'm with Jaros yikes solder rules power perfect

an hey i like the smell of solder playful

Have to go with the solder over crimped thumbsup
Especially if vehicle sees any salt environment
One dunking in sea water and crimps are toast

2 users like this post: Jaros, HeadsUp

#43

ctxkid
Member
From: Up Ship Creek
Joined: 12 April 2018
Posts: 2,146
Member
25 January 2019 11:50 am

bicter wrote:

Use of a DC-DC can be justified when the second battery has a charge profile unsuited to paralleling the start battery or other requirements demand it, such as if an unregulated solar panel is required to keep the 2nd battery charged

paralleling the start battery is great for battery sales thumbsup clap


...................................................Such is life........................................................
Oldest Copper coin 1799 left seated half penny, Oldest Silver 1834 Shilling

#44

Ded Driver
Member
From: West of the Border, WA
Joined: 27 May 2018
Posts: 1,936
Member
25 January 2019 02:27 pm

Dog Ranger wrote:
Ded Driver wrote:

update: Im very happy with my system so far. Lead Crystal battery + Projecta 45A DC-DC charge controller + 100W solar panel
Im finding the solar panel more than covers my fridge on sunny days, and tops up the battery. I have a dual voltmeter on the circuit shows me battery & solar input.
I have a manual circuit breaker under the bonnet between the 2 batteries (for alternator charging), & i flick this in once a week or so to ensure ther battery gets a full current top-up as required. Im still procrastinating on whether or not to install the solenoid that I have .... I like manual operation on most stuff, plus still need a breaker/fuse anyway.
An interesting point on the LC battery ... my electronic diagnostic unit (analyses battery & alternator charging, & has proven correct on many occassions now) cannot analyse the Lead Crystal Battery, I assume due its different chemical makeup.

Given your running a DC D.C. unit any specific reason for manually disconnection from alternator? Just curious?

struth, hard to keep up with the string of comments running here last couple of days.
Dog Ranger, the disconnect isnt essential, but most of the time it is uneccesary to be drawing from the alternator, as the solar panel will catch up with demand over a day, & this saves wear on the alternator (plus a microscopic amount of fuel). & given the amount of kms i do & a lot of night driving with a lot of light, I do wear alternators out!
As to other queries/comments about solar voltage, I did my research & checked that my solar panel max V (23V) is less than what the IDC45 accepts (28V).
The IDC45 has a separate solar input with mppt control. It is mounted in the back next to the aux battery. To minimise voltage drop I have a 175A cable running from front to rear that only ever sees a max ~45A that the IDC pulls.

Last edited by Ded Driver (25 January 2019 02:40 pm)


APLA member, GPX4000, modded SD2100, XTerra705, GM1000, Whites MXT Pro, Nokta Pointer, sP01 Enhancer, Garmin GPSMAP 64S, kti PLB, a map, all sorts of coils & a cupla buckets full of hope & enthusiasm

#45

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
25 January 2019 09:07 pm

ctxkid wrote:
bicter wrote:
ctxkid wrote:

Flood solder all connections cool

Or crimp to the design pressure ensuring the correct cable size for the connector and the correct crimp tool is used.

i have seen to many poor crimped connections awful

i'm with Jaros yikes solder rules power perfect

an hey i like the smell of solder playful

No argument with me on soldering. Trained to NASA spec in soldering but that was long long ago.

My comment was regarding the statement in the article Jaros posted where the author stated "crimp and solder"
It should have been "either/or" not "and".

My preference is to solder over crimp as it is too difficult to get the correct matching of tool, cable and crimp pin for small quantities.

Crimps do have their place in wiring provided they have been done correctly.

With regard to crimps in salt environment, I think that if a crimped DC connection is having problems within a salt environment, every connector used in that car is going to have the same issue... or am I missing something?

1 user likes this post: Dog Ranger

#46

Rockhunter62
Member
From: Roaming, WA
Joined: 03 May 2016
Posts: 2,214
Member
25 January 2019 09:30 pm

"No argument with me on soldering. Trained to NASA spec in soldering but that was long long ago."

Not ex RAAF are you bicter? Same here.

Cheers

Doug


Forest Gump once said "life is like a detector going beep, you don't know what it is till you dig it up"

#47

condor22
Member
From: Adelaide, SA
Joined: 16 December 2013
Posts: 1,579
Member
25 January 2019 11:25 pm

Yup, ask any RAAF Instrument Fitter how they terminate wires in pins n sockets. We just drive ours down the road at 100kph, their wiring travels a "little" faster smile a "little" higher smile and "little" more temperature variation smile

Amazing what can be learned standing behind one of those guys......

1 user likes this post: HeadsUp

#48

bicter
Member
Joined: 28 August 2013
Posts: 73
Member
26 January 2019 07:41 am

Rockhunter62 wrote:

"No argument with me on soldering. Trained to NASA spec in soldering but that was long long ago."

Not ex RAAF are you bicter? Same here.

Cheers

Doug

Yep, saw the light and got out after 6 years in '81 as a RadtechG but stayed in the aviation world for the next 35 years. Spent most of my time between Melbourne and Darwin.

1 user likes this post: Rockhunter62

#49

Dog Ranger
Member
Joined: 07 December 2018
Posts: 150
Member
26 January 2019 08:12 am

With regard to crimps in salt environment, I think that if a crimped DC connection is having problems within a salt environment, every connector used in that car is going to have the same issue... or am I missing something?

In my limited experience one has found not all vehicle wiring has the same exposure to the element's?
As an example a connection behind the dash and an under bonnet connection due to this live in different worlds hey ?
One you could call a friendly environment the other being harsh sad
Different experience leads to differing opinions . Probably none right or wrong just do according to suit ones needs.
Happy Oz day smile

#50

ctxkid
Member
From: Up Ship Creek
Joined: 12 April 2018
Posts: 2,146
Member
26 January 2019 02:11 pm

the figures i agree with , good read perfect

https://www.energymatters.com.au/compon … discharge/


...................................................Such is life........................................................
Oldest Copper coin 1799 left seated half penny, Oldest Silver 1834 Shilling

1 user likes this post: Ded Driver

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